Electromechanical devices of this type are already known, which comprise a first connection for a source of power, a second connection apt to be connected to a load supplied by said source of power and means for controlling the intensity of the current traversing the load, these control means comprising a variable resistance circuit connected between the first and the second connections, as well as mechanical means apt to vary the resistance of the resistance circuit.
In this manner the intensity of the current traversing the load can be made to vary and, in the event this load is a motor, the speed of said motor can be made to vary.
In the case of a device of this type applied to set the speed of the motor of a fan in a motor vehicle, the control means generally comprise a multi-position switch having one control arm apt to co-operate with a given number of terminals each of which is connected to the motor by an electrical connection comprising an electric wire and a resistance of definite value.
By acting on the switch, the arm is made to co-operate with a selected terminal, this making it possible to establish an electrical connection with the motor across the corresponding resistance.
In this manner the speed of the motor can be given a value chosen from among a limited number of values, each of which is defined by an appropriate resistance. For example, the speed of the motor can be set between a zero speed, a low speed, an intermediate speed and a high speed.
In known devices of this type a multiplicity of electrical connections is required, therefore also a large number of electrical wires between the switch and the fan motor.
This makes it necessary to have a great length of wire and may lead to inverted connections and the corresponding installation is disassembled and then reinstalled.
Moreover, inasmuch as the switch is located in the instrument panel of a vehicle, while the fan motor is housed in a box located at a distance from this instrument panel, the electrical wires form a bundle of great length for which a passage between the instrument panel and the fan housing must be provided.
Finally, the terminals or contacts located in the instrument panel are not cooled and can become damaged or yet deteriorate under the effect of the heat released.